Conventional automotive fuel injectors for an internal combustion engine include an inlet tube, a needle valve assembly, including an armature, an electromagnetic coil, a fuel delivery nozzle, and a biasing spring to bias the needle valve assembly in a closed position relative to the nozzle. When the electromagnetic coil is energized, a magnetic force is generated which operates against the action of the biasing spring to open the needle valve assembly. During fabrication and assembly of the injector, the needle valve assembly may become misaligned relative to the inlet tube, which may interfere with the biasing spring and effect the operation and durability of the injector.
In particular, the inventors of the present invention have found that this misalignment causes conventional biasing springs to rub against the sides of the inlet tube or the needle valve assembly. This may result in excess wear on the needle valve assembly or the inlet tube potentially causing a premature failure of the fuel injector. In addition, the spring itself may wear prematurely. This could change the design parameters of the fuel injector, namely the fuel injector opening force, resulting in a change in the amount of fuel delivered to engine. Prior art fuel injectors attempt to prevent the effects of this misalignment by fixing the biasing spring at one end to the inlet tube and at the other end to the needle valve assembly. This results in a relatively expensive and difficult to manufacture fuel injector. Other attempts to prevent rubbing of the biasing spring against the needle valve assembly or inlet tube (where the needle valve assembly or inlet tube includes a relief) results in a fuel injector having a larger electromagnetic coil to accommodate for the reduced magnetic force associated with reduced ferromagnetic material in the area of the biasing spring.